Field-free Spin-Orbit Torque Perpendicular Magnetization Switching Induced by Metallic Multilayers.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Spintronics

Background:

• All-electrical manipulation of perpendicular magnetization switching is key for advanced information storage and spintronic devices.
• Current-induced spin-orbit torque (SOT) is a promising method, but often requires external magnetic fields, hindering practical applications.

Purpose of the Study:

• To investigate spin-orbit torque (SOT) in [Pt/Au] multilayers with a compositional gradient.
• To achieve current-induced, field-free perpendicular magnetization switching in spintronic heterostructures.

Main Methods:

• Fabrication and characterization of [Pt/Au] multilayer films with compositional gradients.
• Measurement of SOT efficiency and anomalous Hall resistance loops.
• Control experiments to identify the source of spin current polarization.

Main Results:

• The [Pt/Au] multilayer demonstrated significantly enhanced SOT efficiency compared to pure Pt.
• Current-induced, field-free perpendicular magnetization switching was successfully realized in Co/[Pt/Au] heterostructures.
• Anomalous Hall measurements confirmed the generation of a z-direction polarized spin current, primarily attributed to the Pt/Au interface.

Conclusions:

• The Pt/Au interface plays a critical role in generating the z-direction polarized spin current necessary for field-free switching.
• Field-free switching is likely driven by a synergistic interface effect and Dzyaloshinskii-Moriya interaction.
• This research advances SOT devices toward practical applications and offers new insights into magnetization switching mechanisms.